Electrical Circuit Load Calculator

Calculate electrical circuit load parameters including current draw, power consumption, resistance, and voltage drop for both AC and DC circuits.

Formulas Used

DC Current: I = P / V

AC Single-Phase Current: I = P / (V × PF)  |  S = P / PF  |  Q = √(S² − P²)

AC Three-Phase Current: I = P / (√3 × V × PF)

Wire Resistance (round-trip): R = ρ × 2L / A   where ρCu = 1.724 × 10⁻⁸ Ω·m

Voltage Drop (DC / 1-phase): Vdrop = I × Rwire

Voltage Drop (3-phase): Vdrop = √3 × I × Rwire

Wire Power Loss: Ploss = I² × Rwire

Assumptions & References

  • Copper conductor resistivity: 1.724 × 10⁻⁸ Ω·m at 20 °C (IEC 60228).
  • Wire cross-sectional areas follow standard AWG sizes (ASTM B258).
  • Voltage drop uses round-trip wire length (2 × one-way length) for DC and single-phase AC.
  • Three-phase voltage drop uses the line-to-line formula: Vdrop = √3 × I × R.
  • NEC 80% continuous load rule applied per Article 210.20(A) and 215.2(A)(1).
  • Maximum recommended voltage drop: 3% for branch circuits (NEC 210.19 informational note).
  • Power factor applies only to AC circuits; DC circuits assume unity power factor.
  • Skin effect, temperature derating, and conduit fill are not accounted for.
  • Results are for estimation only; consult a licensed electrician for installation design.

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